1. Field of the Invention
The present invention relates to a data communication system, an apparatus and a method therefor and a program contained in a computer-readable medium for confirming the network connection relationship, and more particularly to a technology for managing the network constructed through a digital interface for communication.
2. Related Background Art
With the recent development of digital audio-visual equipment such as a digital camera or a digital video camera, there is being developed a technology of constructing a network by connecting the peripheral equipment (printer, hard disk etc.) of the personal computer (hereinafter represented as PC) and such audio-visual (AV) equipment through a common digital communication interface.
Among the technologies employable in such communication system, there is already known the IEEE 1394 standard (IEEE Standard 1394-1995, represented hereinafter as IEEE 1394 Standard) relating to the high performance serial bus.
The communication interface based on the IEEE 1394 Standard (hereinafter represented as 1394 interface) is a digital interface capable of bidirectional communication and is capable of serially transmitting data packets at a high speed. The 1394 interface has the following features:
(1) It has two transfer modes, namely the isochronous mode and the asynchronous mode. The isochronous mode, guaranteeing the transmission and reception of a predetermined amount of packets within a communication cycle time (125 .mu.s), is effective for real-time transfer of the image data or the voice data. The asynchronous mode transmits and receives the control commands and the files when necessitated in asynchronous manner, and has a lower priority in comparison with the isochronous mode; PA1 (2) It has a higher freedom of connection, allowing to use the daisy chain system and the node branched system in mixed manner and enabling to construct a network of higher freedom; PA1 (3) It is capable of automatic recognition of the network configuration. More specifically, the interface is provided, in response to a change in the network configuration caused by the start or termination of the power supply or by the addition or deletion of an electronic equipment, with a function of automatically setting and recognizing the ID information set on each electronic equipment on the network; and PA1 (4) There can be employed a finer cable with smaller connectors, since the data transfer between the 1394 interfaces is conducted in serial manner. PA1 a) display means for displaying the connection relationship of the plural equipment; PA1 b) designation means for designating a specified equipment displayed by the display means; and PA1 c) communication means for effecting, with the specified equipment, a communication for confirming the connection relationship with the specified equipment according to the designation by the designation means. PA1 a) display means for displaying the connection relationship of the plural equipment; PA1 b) designation means for designating a specified equipment displayed on the display means; and PA1 c) communication means for effecting, with the specified equipment, a communication for controlling the function of the specified equipment, according to the designation by the designation means. PA1 a) reception means for receiving confirmation data, transmitted by a predetermined equipment, for confirming the connection state; and PA1 b) display means for effecting a display indicating the reception of the confirmation data. PA1 a) communication means for recognizing ID information set on an equipment connected to a data bus and effecting communication utilizing the ID information; PA1 b) generation means for generating inquiry data for inquiring the equipment information of the equipment indicated by the ID information; and PA1 c) preparation means for preparing a table showing the correspondence between the ID information and the equipment information, based on a response to the inquiry data transmitted by the communication means. PA1 a) detection means for detecting the signal flow among the plural equipment; and PA1 b) display means for displaying, together with the equipment information of the plural equipment, channel information indicating the signal flow among the plural equipment. PA1 a) a display step of displaying the connection relationship of the plural equipment; PA1 b) a designation step of designating a specified equipment displayed by the display step; and PA1 c) a communication step of effecting, with the specified equipment, a communication for confirming the connection relationship with the specified equipment according to the designation by the designation step. PA1 a) a detection step of detecting the signal flow among the plural equipment; and PA1 b) a display step of displaying, together with the equipment information of the plural equipment, channel information indicating the signal flow among the plural equipment. PA1 a) display means for displaying the connection relationship of the plural equipment; PA1 b) designation means for designating a specified equipment displayed by the display means; and PA1 c) communication means for effecting, with the specified equipment, a communication for confirming the connection relationship with the specified equipment according to the designation by the designation means. PA1 a) a first data communication apparatus equipped with communication means for transmitting confirmation data for confirming the connection state in the data communication system; and PA1 b) a second data communication apparatus equipment with display means for effecting a display indicating the reception of the confirmation data. PA1 a) a display step of displaying the connection relationship of the plural equipment; PA1 b) a designation step of designating a specified equipment displayed by the display step; and PA1 c) a communication step of effecting, with the specified equipment, a communication for confirming the connection relationship with the specified equipment according to the designation by the designation step.
FIG. 1 shows a digital communication system constructed with plural electronic equipment provided with the 1394 interfaces mentioned above.
In FIG. 1, there are a printer 101, a personal computer 102, a digital video tape recorder A (DVTR-A) 103, a digital video tape recorder B (DVTR-B) 104 and a video disk 105. These equipment are connected through communication cables 106 based on the IEEE 1394 Standard.
In the communication system shown in FIG. 1, the 1394 interface constantly monitors the change in the configuration of the connections, caused by the start or termination of the power supply in each equipment or by the addition or relation of the equipment, and, upon detecting a change in the configuration (topology), the 1394 interface of each equipment automatically executes a process of recognizing the network topology and providing each equipment (hereinafter called node) with the ID information (hereinafter called node ID).
The recognition of the configuration of the connections is executed, after a bus resetting (initialization of the bus with clearing of the information on the connection configuration), by the declaration of the mother-daughter relationship by the nodes. By the determination of the mother-daughter relationship among the nodes, the nodes recognize the connection configuration of the network in the form of a tree structure (hierarchic structure). An equipment which becomes the mother (or highest rank) of all the equipment constitutes a root node and manages the mediation of the bus use right.
After the determination of the root node, the network automatically sets a physical address (namely node ID) for each node. The setting of the node ID is basically executed a process in which a mother node permits the setting of a physical address to a daughter node connected to a communication port of a smaller port number and then such daughter in turn permits the setting of physical addresses in succession to its daughter nodes. After the ID setting in all the daughter nodes, the mother node sets its own node ID.
In the following there will be explained the automatic setting process of the node ID's, with reference to FIG. 1, in which the personal computer 102 is assumed to become the root node after the recognition of the connection configuration.
Referring to FIG. 1, the PC 102 constituting the root node at first permits a node connected to the communication port of a port number "#1", which is the printer 101, to set the node ID. The printer 101 sets "No. 1" as its own node ID and transfers this result, by a self ID packet, to all the equipment on the bus (broadcasting). As a result, all the equipment on the network recognizes that the "node ID No. 0" is already assigned, and an equipment which next obtains the permission for the node ID setting selects No. 1.
After the node ID setting of the printer 101, the personal computer 102 permits a node connected to the communication port of a port number "#2", which is the DVTR-A 103, to set the node ID. The DVTR-A 103 in turn gives permissions to daughter nodes (DVTR-B 104 and video disk 105) in the increasing order of the port number of the communication ports, namely in the order of the DVTR-B 104 at first and then the video disk 105. The DVTR-B 104 and the video disk 105 set the node ID's "No. 1" and "No. 2" in succession and then broadcast self ID packets. After the node is setting of the DVTR-B 104 and the video disk 105, the DVTR-A 103 sets its own node ID as "No. 3", and finally the root node (PC) 102 sets its own node ID as "No. 4" whereby the recognition of the connection configuration is completed.
The 1394 interface is provided with two transfer modes, namely the asynchronous transfer mode and the isochronous transfer mode. An asynchronous packet is composed of a header portion, a header CRC, a data portion and a data CRC. The header portion contains address ID information (node ID of the addressee node), source ID information (node ID of the packet transmitting node) and various control information, and the asynchronous packet is transferred to a node designated by the address ID information. The node receiving the asynchronous packet always returns an acknowledgment but does not return the acknowledgment if it is a broadcast packet.
An isochronous packet is composed of a header portion, a header CRC, a data portion and a data CRC. The header portion contains channel number information (a number given to a band width capable of transferring the isochronous packet) and various control information. The isochronous packet is not transferred to a specified node but broadcast to the entire bus. Consequently each node can receive the predetermined isochronous packet by detecting the channel number. The node receiving the isochronous packet does not return the acknowledgment.
However, the communication system constructed with the above-explained 1394 interfaces has been associated with the following drawbacks.
The 1394 has the advantage capable of adapting to the daisy chain system and to the node branched system in order to achieve a high freedom of connection. However, in case a complex network is constructed by connecting plural electronic equipment in succession, the user becomes unable to identify the position of the desired electronic equipment within such network.
Also in case of a failure in a communication cable or a connector in such network, the user is unable to recognize the position of such failed connection.
Furthermore, it is very difficult for the user to recognize all the signals inputted into and outputted from these equipment.